Generally, when a photo resist is coated on a surface of a thin plate-shaped work and an exposing operation is performed by utilizing a contact aligner, after a photomask is held and fixed by a mask holder which is disposed at upper portion of a work stage, then, the thin plate-shaped work is held and fixed on the work stage by vacuum sucking (vacuum absorption) thereby to adjust an alignment of the work. Thereafter, the exposing operation is performed. In this connection, in order to vacuum-suck the thin plate-shaped work on the work stage, a vacuum sucking hole is provided at an arbitral position on the work stage, and an entire rear surface of the thin plate-shaped work is contacted to the work stage, so that the thin plate-shaped work is held in a horizontal state.
However, as disclosed in a Patent Document 1, in a conventional exposing step of a thin plate-shaped work of which both sides are to be worked, for the purpose of preventing contamination and damage of the entire rear surface of the thin plate-shaped work, it is not possible to contact the entire rear surface of the thin plate-shaped work to the work stage. Therefore, it is necessary to hold and fix the thin plate-shaped work at only a projected mounting portion provided to the peripheral portion of the thin plate-shaped work. Accordingly, there has been generally adopted a method in which the thin plate-shaped work is held and fixed by vacuum-sucking at a vacuum sucking hole formed in the projected mounting portion which is provided to the peripheral portion of the thin plate-shaped work.
Further, in case of the thin plate-shaped work of which both sides are to be worked, it is necessary to perform a both-side alignment in which a mask pattern and a pattern of rear surface of the thin plate-shaped work are aligned in addition to a single sided alignment in which the mask pattern and a pattern of front surface of the thin plate-shaped work are aligned, this single sided alignment being usually performed in the single sided work. In the above single side alignment, there has been normally used a method in which the mask pattern and the a work pattern are simultaneously observed by means of a microscope provided to an upper portion of the work stage, and a pattern adjusting is performed by moving the thin plate-shaped work. Furthermore, in the above double sides alignment, there has been generally adopted a method in which firstly only the photomask is contacted on the work stage by means of a microscope provided to a lower portion of the work stage whereby a position of the mask pattern is memorized and stored by the microscope. Thereafter, the photomask is raised without moving the microscope, and the thin plate-shaped work is held and fixed on the work stage, then the pattern of the thin plate-shaped work and a memorized pattern of the photomask are adjusted.
Further, in an exposing step after the aligning step, the following three kinds of exposing methods are mainly adopted. Namely, there have been used: a proximity exposing method in which a gap (proximity gap) is provided between the photomask and the thin plate-shaped work, and the exposing operation is performed in this state; a soft contact exposing method in which an exposing operation is performed in a state where the mask holder and the work stage are mechanically contacted to each other; and a hard contact exposing method (for example, see Patent Document 2) in which an exposing operation is performed in a state where a close contacting property between the photomask and the thin plate-shaped work is enhanced by a force of vacuum or fluid or the like from the soft contact state. As one example of this hard contact exposing method, there is a method in which a fluid is introduced from the vacuum suction hole provided to the peripheral portion of the work or the fluid is introduced from a central portion of the thin plate-shaped work thereby to enhance the close-contacting property between the thin plate shaped-work and the photomask.    Patent Document 1: Japanese Patent Provisional No. 2004-61280    Patent Document 2: Japanese Patent No. 3362653